Radiorepeater



Jan. 15, 1929.

R. BOWN nAmo REPEATER 2 Sheets-Sheet 1 Filed Nov. 8, 1924 INVENTOR[1h40/v mz Patented Jan. 15, 1929.

NITED STATES PATENT OFFICE.

RALPH BOWN, OF MAPLEWOOD, JERSEY, ASSIGNOR TO AMERICAN TELEPHONE .ANDTELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

RADIOnririzincrri1t.

Application led November 8, 1924. Serial No. 748,738.

' This invention relates vto radio repeater systems, and particularly toa system of that type characterized by undirectional reception at therepeater station and having separate receiving circuits, each of thelatter Vhaving gain control devices whereby the transmission level ofthe oppositely directed channels may be separately controlled, the saidsystem being furthercharacterized byla single antenna structure fortransmitting bot-h channels.

Various types of radio repeaters have been devised, one of which, knownas the QQ-type, embraces, in fact, two complete transmitting andreceiving stations. One stationreceives, for example, from the West andvtransmits to the east and the other operates only in the oppositemanner. A repeater system of that type requires, in the most generalcase, the use of four channels or frequency bands in order to eiiecteast and west two-way trans-v mission witliout interference. Such asystem is, however, expensive to install and operate and is also open toother criticism. It possesses, however, by virtue of the use of separatetransmitting and receiving apparatus for the oppositely traveling waves,the advantage that the said oppositely traveling waves may be separatelyamplified to a degree depending upon the transmission losses of theseparate waves.

Another type of repeater, known as the 21- type, employs only a singletransmitting and receiving station and utilizes two channels. Both theeast bound and west bound signaling waves come to a singlereceiver uponthe same carrier frequency, and both waves are repeated from thesame'transmitter at the same carrier frequency, the transmittingfrequency, however,'being different from the received carried frequency.While such a system is simple and cheap it has certain transmissiondefects which limit its usefulness, the principal one of which is thatthe repeater, having no flexibility of adjustment, amplifies equallyboth the eastbound and the westbound signaling waves.

The object of my invention is to provide a Ql-type repeater withindependent unidirectional receiving` systems so that two incomingVmessages on the same wave length, but from different directions, may bereceived separately andy each may be brought to any desired relative vorabsolute transmission level before they are reradiated from a commontransmitting circuit.

Other objects of this invention will be apparent from the followingdescription when read in connection vwith the attached drawing of whichFigure 1 shows schematically one form of the embodiment of the inventionemploying unidirectional receiving antennae of the combined vertical andloop type; Fig. Y

2 shows the characteristics of the receiving antennae; and Fig. 3 showsa system employing a wave antenna, the receiving characteristics ofwhich are as shown in Fig. 2.

In Fig. 1 is disclosed a system employing two terminal stations A and Band a single repeater station located therebetween. At the left the lineL1 connects the signaling apparatus 1, which may be a subscriberstelephone set, with the terminal station A, the connection beingeffected by means of the hybrid coil 3. The network N, connected withthe hybrid coil 3 balances the line L1. In similar manner, the line L2connects the telephone set 2 with the terminal station B, the connectionbeing effected by means of the hybrid coil 19 to which is also connectedthe network N2 to balance the line L2. The hybrid coil 3 sometimes knownas a three-winding transformer has windings connected with the line andalso with the network and another winding 4 connected by the circuit 5with the radio transmitter 6. The radio transmitter may be of any wellknown type comprising `a source of carrier current whose wave lengthis)el and means to modulate this carrier current with the signalingcurrents impressed upon the radio transmitter by thev hybrid coil. Thistransmitter'may also include one or more stages of amplification and mayhave selective means such as the Campbell wave filter. The radiotransmitter 6 is connected wit-li the antenna 7 which need not be of aunidirectional type. The receiving branch of this terminal circuitcomprises an antenna 15, which need not be of a unidirectional type, anda radio receiver having its inof receiver would preferably have one orvmore stages of ainplii'ication and also selec` tive devices. f

The repeater station embraces separate receiving circuits and a:-common*transmitting.

circuit. The receiving circuit tor the Waves transmitted from antenna 7comprises a unidirectional antenna structure yconsisting ot ai verticalantenna7 8 coupled With a4 loop antenna 9, which structure is connected.with the radio receiver 10. ri`he reception characteristic of thisantenna is represented by X of Fig. 2. The form oi radio'receiver usedmay-be that in Whichtlie incoming frequencyy isbe'aten down: toa' lowerlevel before being impressed upon'tlie ainpliiier and gain controlapparatus-r11.. Bymeans of the device 11V the required degree ot'ampliiication may be lgivenetothe-received Waves, and they may then beimpressed-upon the radio transmitter 12 Whereinthey are beaten toproduce a fie quency corresponding; to the Wavelength )r2 and aretransmitted by the antenna 13;. Since the antenna 13- is not directive,these Waves Will ale'ct both antenna. 15 at stationv A and antenna 111at station B. The resultant incoming Waif'esat: station A Will beimpressed upon the line L, and will beheard as a sidetone bythesubscriber at station 1; rEhe transmitted WavesV received by antenna 14Wili be impressed upon the radio receiver 17, and atterdemodulation,andk preferably amplitication, will be impressed by the circuit 18 uponlthe line Lo through the hybrid-coil 19 and? Will be heard by. thesubscriber at; sta.-y tionV 2.

. The: repeater station also comprises a di rectional antenna structureconsisting ofthe vertical antenna 23- and the loop antenna 24',

which structure is connected with the radioy seen that speech signalsimpressed upon the line L, by the'apparatus 1=Will modulate carL riercurrents ofthe'wave lengtha, by. means of the radio transmitter 6, andthe modulated vvaves will be radiated by the antenna 7. These highfrequency Waves as thus modu-Y lated Will be received by the antennastructure 8 9, and will be beaten with another frequency Within theradio receiver 10. One of the resultant frequencies or bands will beselected and given the requisite amplification by means of the device11. rl`his will be impressed upon the radiol transmitter 12 andWilltherein'be beaten Wit'l'ranother frequency, sol that one of theresultant frequencies will correspond to the transmitting Wave lengh a2.This wavelength, modulated by the speech currents, will be transmittedby the antenna 13 an'd'vvill? aiiect antennae 1e and 15 in the mannerreferred to above. That which ahlects antenna 15K Will be deinodulatedby the receiver. 16, andthe speech current Will fioiv over the line L1to the station 1 appearing therein asa side tone e'decaand the partaffecting antenna 11i will be demodulated by the receiver 17,V and thespeech coniponentivill be transmitted by the line L., to station 2. Thespeech currents setup at station 2 will be conveyed by the line L2 tothe station Band Will be impressed upon the radio transmitter 21servingtherein to modulate the carrien current corresponding to theWavelength a1. This ycarrier current, as thus modulated, Will beradiated from the antenna 22and will atectthe lantenna structure 23-24but will produce no substantial ciiiect upon the yantenna structure 8 9because the latter receives only slightly from the direction of terminalstation B. rlhe modulated Waves from the structure 23-2li Will bedeinodulated'by theradio'receiver 25 and impressed upon the amplifier 26ivherein it Will be given the necessary ampliiication, and the resultantamplified current will be impressed upon the radio-transmitter 12.. Theresultant modulated high frequency current cor esponding to the Wavelength )r2 will be 'transmitted broadly, aiiiecting antennae 14 and 15.rlie part affecting antenna 11i produces a side tone etlect at thesubscriber station 2.v The part aiiecting antenna. 15 Will bedeiiiod'ulated by the receiver'1l6, and the resultant low frequencycurrent Will reach the receiver of the subscriber station 1. l

By using diierent transmitting and receivingivave lengths, theindividual terminal circuitsA are prevented from singing. The tendencytosing` is furthermore minimized by the use of the hybrid coil and thenetwork at each terminal station to balancetheline circuitconnected'thereivith, and in lilre'inanner, the-tendency of therepeater'circuit' to sing is reduced to a minimum. Although the sameWave length has been'employed in transmitting from stations ik and B andalso the same'WavelengthV in transmitting from Jthe repeaterstation toboth stations A. and B, l ain able to control the-magnitude ofampliiication to be given to the oppositely traveling waves by usingunidirectional receiving antennae, each of which has its separateamplifyingand gain controlling apparatus.

Another form of this invention is shown in Fig. 3. The structure of thisfigure differs from that of 1 principally inthe use of a wave antennainstead of the combined vertical and loop antenna structure shown inFig. 1. The same reference characters have been used in Fig'. 3 toindicate parts similar to those shown in Fig. 1. Since the terminalstations are similar to those shown in Fig. 1 the description of theapparatus will be limited to the repeater station. The antenna 30, whichreceives independently from two opposite directions upon the same wavelength, is described in a paper by Beverage, et al., entitled The waveantenna published in the Journal of the American Institute of ElectricalEngineers, Vol. XLII, Nos. 3, 4L, 5 and 6. The forni used by theapplicant is subtantially the same as that shown in Fig.13 of the saidpaper. This antenna comprises two conductors connected with the outerterminals of the coils 30 and 33. The midpoint of coil 3() is connectedto ground through the winding 32 which is coupled with the winding 35connected with the input side of the radio receiver 10. Coil 33 has itsmidpoint connected to ground through coil which is inductively connectedwith coil 33 so as to reflect the wave from the transformer 33-34whenever current flows through coil 34 to ground. This constitutes therefiection transformer described by Beverage at page 264,- of the papercited above. Coil 30 is coupled with coil 31 which is connected with theinput side of the radio receiver 25. As will be clear from a laterdescription, radio receiver receives, detects and ampliiies to therequired degree the waves transmitted from station A and, in likemanner, radio receiver affects those waves transmitted from staH tion B.The output sides of both of these radio receivers are connected with thehybrid coil 37 which is connected with the radio transmitter 12 and alsowith the network N3, the purpose of which is to balance the transmittingcircuit, including the radio transmit# ter 12 and the antenna 13. Bymeans of the transmitter l2, the high frequency current is modulated bythe currents impressed thereon by the radio receivers l() and 25 inorder to effect transmission of the latter currents to the receivingantennae at stations A and B. The antenna 8O is so arranged that whenthe electromagnetic waves from station A are impressed thereon currentwill flow to ground from thc two conductors thereof through the midpointconnections of coils 33 and 30. Since the current flows in oppositedirections in coil 30, no effect will be produced thereby in coil 31which is connected with the input side ofthe receiver 25. But thecurrent flowingfrom the midpoint of coil' 30 through coil 32 willproduce an effect in coil 35 which will 'beimpressed upon the radioreceiver 10. This current will be demodulated either entirely, i. e.,t-o produce a. speech frequency, or partially to produce an intermediatefrequency modulatedl by the speech frequency. Y Regardless of t-heextent of demodulation, the demodulation current will be amplified tothe degree required in order to produce the proper transmission levelfor the transmitted wave. The amplified current will be impressed bywinding 36 upon t-he hybrid coil 37and will, in turn, be impressed uponthe radio transmitter 12. Herein it will serve to modulate carrierfrequency so as to produce a modulated high frequency currentcorresponding to the wave length A2. This will be radiated by theantenna 13 in both directions and will produce currents in thesubscribers sets connected with the lines Ll and L2. The wavetransmitted from antenna 22 at station B will be reflected in theantenna 8() from the end connected with the coil and will produce themaximum voltage at the end connected with coil 33. The effect thereof isto cause a circulation of current around the conductors and through thecoils 30 and 33. This current will be impressed by Coil 31 upon theradio receiver 25 but will not flow to ground through the branchcontaining coil 32. Consequently the waves transmitted from antenna 22will not affect receiver 1() which is intended for operation only inconnection with stat-ion A.

It will be seen, therefore, that by means of the arrangement shown inFig. 3 the oppositely traveling waves may be given independentamplification, the degree of which depends upon the relative losses ofthe oppositely traveling waves. The arrangement is furthermorecharacterized by the use of a single antenna coupled with separatereceiving circuits in such manner that each receiving circuit will notbe affected by waves impressed upon the antenna from a direction otherthan from which they are intended to receive. The arrangement is alsocharacterized by the use of the hybrid coil and balancing network of therepeater stat-ion whereby the undesired reaction between the two radioreceivers is prevented.

vWhile this invention has been disclosed as embodied in a particularform, it is tok be Y the said antenna in such manner that euch Willreceive Waves only from a predetermined direction, the said translatingcircuits having means to detect the received frequencies and to amplifythem to the required degree, and a transmitting circuit common to thesaid translating circuits adapted to modulate the amplied currents andto transmit them.

In testimony whereof, I have signed my 10 name to this specificationthis 7th day of November 1924.

RALPH BOVN.

